Galvanometer construction



Dec. 28, 1954 C, M HATHAWAY 2,698,417

GALVANOMETER CONSTRUCTION Filed Sept. 14, 1950 @haak MK2/Mayday UnitedStates Patent O GALVAN OlVIETER CONSTRUCTIDN Claude M. Hathaway,Littleton, Colo., assiguor to Hathaway Instrument Company, Denver,Colo., a corporation of Colorado Application September 14, 1950, SerialNo. 184,868

3 Claims. (Cl. 324-97) The present invention relates to a galvanometerconstruction whereby a large number of galvanometer elements can belocated in a relatively small space.

For certain oscillograph purposes it is desired to provide a relativelylarge number of oscillograph elements or galvanometers so as to providea compact arrangement. It further is desired to provide moving elements,which may be damped with oil, if desired. In the past arrangements ofthis kind have employed a single relatively large permanent magnet withindividualized pole pieces for the several galvanometer elements.

In order to Yprovide for convenient replacement of any element deemed tobe defective or inaccurate, it would be desirable to provide an improvedgalvanometer wherein connections are readily made thereto. Itfurthermore would be desirable to have an improved magnet design whichis not quite so bulky and which provides pivotedadjustment of thegalvanometer element in a vertical plane.

Other and further objects of the present invention will subsequentlybecome apparent by reference to the following description taken inconjunction with the accompanying drawing wherein:

Figure l is an end view of a galvanometer constructed in accordance withthe present invention;

Figure 2 is a front view of the multi-element galvanometer shown inFigure l.

Figure 3 is an enlarged detailed cross-sectional view of a galvanometerelement employed in the structure shown in Figures l and 2;

Figure 4 is an enlarged cross-sectional view of a portion of the deviceshown in Figure 3 as seen at right angles to that ligure;

Figure 5 is a horizontal cross-section as seen in the direction of thearrows along the line 5-5 of Figure 4; and

Figure 6 is a horizontal cross-section as seen in the direction of thearrows along the line 6-6 of Figure 4.

Referring to Figures l and 2 there is shown a multielement galvanometerhaving end plates 11 and 12 and a front plate 13. These plates aresuitably secured to a base 14 by means of fastening means such as screws15. The base 14 has a stepped portion 16 so as to serve as a locatingdevice for a plurality of pole pieces 17 and 18. The pole piece 17carries a permanent magnet element 19 having a curved surface 21. Thepole piece 18 carries a permanent magnet 22 having a curved surface 23.The curved surfaces 21 and 23 comprise segments of a cylindrical surfacehaving an axis passing through the center of a galvanometer element 24.The galvanometer element 24 comprises a non-magnetic housing 25 carryinga magnetic cradle 26 having surfaces complementary to the curvedsurfaces 21 and 23 of the permanent magnets. suitably supported betweenthe end plates 11 and 12 is a terminal block 27 provided with aplurality of binding posts 28 and 29. Two such binding posts areprovided for galvanometer element 24. The block 27 carries a threadedadjusting screw 31, which engages an upright post 32 carried by thecradle 26. The upper end of the post 32 is connected to a spring 33,which in turn engages a lug on the block 27. Thus the spring biases theelement 24 to a certain position as determined by the adjusting screwdevice 31. By means of diierent adjustment the cradle 26 is rocked inthe cooperating surfaces of the permanent magnets 19 and 22. In order toprovide for adjustment of the element 24 through a horizontal angle arotatable post 34 is provided which 2,698,417 Patented Dec. 28, 1954carries a gear sector 35 for engagement with'a gear sector mounted onthe casing 25 of the element 24.

Figures 3 to 6 inclusive show the details of construction of thegalvanometer element contained within the casing 25. At the lower endthere is provided an insulator 36 which carries a threaded rod 37, whichis engaged by a nut 38 bearing against an insulated washer 39. The innerend of the rod 37 terminates in a hollow bifurcated portion 41 toprovide a socket for a plug connector.

At the opposite end of the tube 25, which is of nonmagnetic materialsuch as brass, an internal threaded portion 42 is engaged by a cap 43,which bears against a packing ring 44. The cap 43 is arranged to beremoved so that access may be had to the element carried within thecasing 25. Within the cap 43 there is an insulator bushing 45 carrying aterminal 46 having at its lower end a hollow bifurcated portion 47,which serves as a socket member. The upper end of the member 46 iselectrically connected to a conductor 48.

Between the bifurcated members 41 and 47 there is located a generallyrectangular frame 49 having a rectangular central opening 51. The frame49 at its top has a central aperture fitted with an insulating sleeve 52and carrying an electrical connector 53, which tits into the bifurcatedsocket 47. The electrical connector 53 is connected to one wire 54 ofthe suspended galvanometer element. At the lower end of the wire 54there is provided a bale 55 carrying a mirror 56. The lower end of thebale 55 is connected to the movable coil 57, which in turn is connectedto a wire 58. The wire 58 is connected to a spring 59 which is fastenedto a connector 61 passing through an insulated sleeve 62 in the centralaperture at the bottom of the rectangular frame 49. The lower end of theconnector 61 engages the bifurcated socket 41.

In the proximity of the moving coil element 57 the outer tube 25 isprovided with magnetic inserts to form two pole pieces 63 and 64 shownin Figure 6. The pole pieces 63 and 64 t into the central opening in thecradle 26 Immediately above the pole pieces 63 and 64 there is provideda lens 65 carried by a lens supporting structure 66 inserted into anopening in the tube 25. At the rear of the tube 25 there is located acylindrical segment 67 having at its lower end a gear sector 68. Thisgear sector is the one which is engaged by the gear sector 35 of theadjusting member 34.

In order to replace any of the various galvanometer elements of thestructure illustrated in Figures l and 2, the entire cylindricalassembly 24 may be removed. Thereupon access may be had to thegalvanometer element per se contained within the tube 25 by removing thecap structure 43. Then by grasping the rectangular frame 49 or the upperend of the connector 53, the frame 49 may be withdrawn from the tube andout of engagement with the lower socket connector 41. 'Thus it will beappreciated that a compact structure is obtained, which is readilyremoved for examination or for repair.

If desired, the inside of the sleeve or tube 25 may be tilled with oilin order to provide oil damping of the moving element 57.

In the construction of the galvanometer elements it has been found thata certain arrangement and method of assembly offers certain advantages.In assembling the apparatus shown in Figures 3 and 4 the housing carriesa lens 65. It might be thought that the leps 65 could be cementeddirectly into an aperture in the housing 25, particularly since it isdesired to orient the lens with respect to the optical path of lightpassing therethrough. This light path extends from the source of lightto the mirror 56 and back to the recording material. It, however, hasbeen found advantageous to mount the lens 65 in a bezel 66 with ashellac base thermoplastic cement. The surfaces of the lens subsequentlyare highly polished. Then the bezel and lens are placed in position inthe housing 25. The bezel 66 is cemented with a synthetic alkyd resincement, such as Glyptal. Just before the cement is quite hard, the lensis oriented with respect to the optical path. While for the purpose ofillustrating and describing the present invention certain preferred foi'saidframe having contacts therein for said connf'zc'torrpins,l on'e ofsaid contacts being connected .to said case andv the vother insulatedtherefrom, Va cradle Yhaving a vertical opening for said case and havingtwo supporting surfaces 'each forming segmental portions 'of ahorizntalcylinder; Va permanent 'magnet structure havingV surfaces' complementaryto said cradle, means for adjustinfgfthe position of said case about theaxis of saidl horizontal cylinder, means carried. by said cradle forrotating said 'case ielativ ther'to about its longitudinal axisincluding a ygear: mounted on said 'cradle arid-a lgear sector mounted'on 'said case. Y

2i galvanometer eleinen't for a multi=element galvanrneter comprising anelongated coil suspended within a non-magnetic rectangular frame',aconne'ctor pin at each end `ofs'aid frame connected to said coil, a-nonmagnetic rcylindrical case having contacts therein to receive said;connector pins, a magnetic cradle' for said case having supportingsurfaces -forming segments of a. ghorizontal cylinder, a' permanentmagnet structure having 'complementary .supporting surfaces for eachcradle, ime'ans carried by `said structure for rocking said 'cradleabout a horizontal axis, "said, 'cylindrical ca'sehav'i'ng onit'snjexterioi: Ya gear sector, a manually adjustable gearmountedfons'aidcradle -for engaging said gear sector to vadjust lsaidcase about a vertical axis, and

magnetic pole pieces carried by said cylinder and extend- 'Ying'fromsaidcradie'- inwardly toward said coil;y f

3.` A galvanometer element for a multi-element galvanometer comprising amovable coil mounted within a rectangular frame, an insulated connectorpin located at each end of said frame and connected to said coil, anon-magnetic cylindrical case' Ili'av'ing contacts therein to receivesaidconnector pins, one of said contacts being connected to" 'said 'easefand the vother contact insulated,

therefrom, a cradle for said casehaving surfacesforming seg'nie'zii'ts-Yof "aflioiz'oiital cylinder, said cradle having a' vertical cyiufdricaiopening, 'a riia'gneficstr'uemre 'having supporting surfacescomplementary thereto, Vsaid struc-V turerincluding permanent magnet,means :carried Yby said structure for rocking said cradle about ahorizontal axis, said cylindrical'case]h''vingl attached to its exteriora gear sector, a manually operable gear mounted on said cradle forengaging said gear sector to rotate said i case about its longitudinalaxis, magnetic `pole piec'es carried by said cylinder and extendinginwardly toward said coil, said pole ,pieces'having exterior surfacescom plementary to the opening-in saidl cradle, a lens -car-r-ied by saidcase,and a mirror mountedv behind said leixs above said coil foractuation thereby.

